Summary Gastroparesis is a disorder of gastric function characterized by delay in gastric emptying, frequently associated with chronic nausea and vomiting, early satiety, postprandial fullness, abdominal pain, and malnutrition that may require nutritional support. The broad objectives of this proposal is to improve our understanding of this disorder and advancing the diagnosis and treatment of gastroparesis and related disorders. We propose to do this through three specific aims, as follows: Specific Aim 1: To maintain, expand, and refine the Gastroparesis Registry in order to enable critical additional and new analyses of the clinical data and biosamples. Specific Aim 2: To conduct a randomized controlled trial of aprepitant in patients with gastroparesis and functional dyspepsia-postprandial distress syndrome. Specific Aim 3: To conduct a pilot and feasibility trial of a potential disease modifying approach using pioglitazone in patients with gastroparesis